/Engine/Source/Runtime/Engine/Classes/Kismet/BlueprintPathsLibrary.h
Assuming both paths (or filenames) are relative to the same base dir, converts InPath to be relative to InRelativeTo
true if OutPath was changed to be relative
static bool MakePathRelativeTo ( const [FString](API\Runtime\Core\Containers\FString) & InPath, const [FString](API\Runtime\Core\Containers\FString) & InRelativeTo, [FString](API\Runtime\Core\Containers\FString) & OutPath )